Microelectronic circuit manufacturers employ various types of automated wiring equipment to electrically interconnect components of a signal processing system architecture. In addition to automated soldering of wires between components, thermosonic ball-bonding (of one mil diameter gold wire, for example) is sometimes used at the device level for connecting an integrated circuit, such as a microprocessor device, to interconnect leads of a support package or substrate.
In accordance with such a conventional thermosonic ball-bonding process, an integrated circuit (typically sized on the order of 0.3".times.0.3"), is placed upon a substrate containing an array of metallized pads that geometrically correspond to the aluminum pads on the surface of the integrated circuit. The substrate is conductively heated to a relatively elevated temperature (on the order of at least 150.degree. C.), usually by way of a heating plate upon which the substrate is supported and clamped, with pressure being applied upon the integrated circuit or attachment substrate.
Ultrasonic vibration (typically on the order of 60 KHz) is then imparted to the clamped structure by means a wire bonding head. During this process, the combination of the application of high temperature, pressure, and the moderate ultrasonic frequency abrasion of the metallic wire against the surface of the terminal pad metal is operative to effect metallurgical atomic diffusion bonding of the gold wire with the metal of the bonding sites.
Now, although thermosonic ball-bonding may be satisfactory for (hermetically sealed) intra-package interconnects at the device level, it is not satisfactory for system level interconnections among substrates and packaged electronic modules, such as antenna panel modules, which may cover a hardware component distribution area greater than 20".times.20", and are to exposed to the ambient environment. A principal shortcoming of a conventional high temperature, ball-bonding process to system-level interconnects is the fact that it is carried out at high temperature. While this may be acceptable for various intra-package lead-connection applications, it cannot be used at the system level, where the application of an elevated temperature, typically on the order of 150.degree. C. or higher, to the system hardware may alter the design parameters of the internal circuitry of its components.
In addition, system level (module-to-module) interconnect, which is typically configured other than a small diameter wire and can be expected to be exposed to the environment, is required to withstand harsh storage, transportation and operating conditions. As a consequence, system level interconnect must be mechanically more robust than the reduced size (one mil) diameter metallic wires used for (hermetically sealed) internal package connections. Moreover, RF signal processing systems require a beam lead type of interconnect, so that the shapes and lengths of the interconnects must be carefully tailored to achieve required impedance matching, so as not to degrade system performance.